About Named Properties Used by Outlook

MAPI provides a facility for assigning names to certain properties, for mapping these names to unique identifiers, and for making this name-to-identifier mapping persistent across sessions. Named properties are identified by a name and a globally unique identifier (GUID) for a property set. The name can be a number or a string. For Microsoft Outlook 2013 or Microsoft Outlook 2010, the property set is often a namespace defined by Outlook 2013 or Outlook 2010, such as PSETID_Appointment.

Named properties are manipulated by using the IMAPIProp::GetIDsFromNames function and the IMAPIProp::GetNamesFromIDs function. The name and the property set GUID are passed to the IMAPIProp::GetIDsFromNames function to obtain a property identifier that is valid for the current MAPI session. Because this property identifier can vary from computer to computer, the only consistent way to access a named property is to know its name and property set GUID.
The range for identifiers is always in the 0x8000 and 0xFFFE range.

Any object that implements the IMAPIProp : IUnknown interface can support named properties. Specifically, a MAPI service provider or a MAPI client must implement IMAPIProp::GetProps to get values of named properties. Setting named properties used by Outlook 2013 or Outlook 2010 is not supported because of the risk of corrupting data that is shared with other MAPI providers or clients.

Outlook 2013 and Outlook 2010 use MAPI named properties to implement many of their features, for example, attachment security and meeting counter-proposals. Above this underlying data, Outlook 2013 and Outlook 2010 expose some of these properties as item properties in their Outlook 2013 and Outlook 2010 object models. For example, the Email1Address property of the ContactItem object in the object model corresponds to the named PidLidEmail1EmailAddress Canonical Property in the PSETID_Address namespace. But in general, due to concerns for compatibility and data integrity, many of the MAPI properties that are used by Outlook 2013 and Outlook 2010 are not exposed in the object model.

This reference describes a number of named properties that are listed below.